This invention relates to an antenna for wireless communication devices. An embodiment of the invention includes a flexible lanyard antenna that is well suited for use with pagers such as interactive messaging pagers or cellular or mobile telephones.
In general, communication devices may be divided into two categories - wireline and wireless. Conventional wireless communication devices utilize the radio frequency (RF) spectrum; however, other medium can be used including, but not limited to, the infrared spectrum and microwave technology. Examples of wireless communication devices include pagers, interactive messaging pagers, telephones, personal digital assistants (PDAs), and the like.
Antennas for wireless communication devices are designed according to ideal physical dimensions that typically correspond to half of a wave length or dipole. For many types of wireless communication devices, however, it may be difficult to achieve these ideal dimensions due to the size of the device or due to the manner in which the device is designed to be utilized. For example, pagers are generally designed to be worn on the belt, or near the waist, of a user and have a display that is designed to be viewed at close to arm""s length, generally from above.
One type of pager that is becoming more common is an interactive messaging pager. Interactive messaging pagers are generally disclosed, for example, in U.S. Pat. Nos. 5,619,531; 5,727,020; 5,764,693; and 5,917,854, the disclosures of which are hereby incorporated herein by reference.
Whereas traditional pagers utilize a receiver and an antenna that permit the pager to receive signals, interactive messaging pagers utilize a transceiver and an antenna and/or antennas that permit the pager both to receive and to transmit. A problem with many interactive messaging pagers is that their antennas are internal and, therefore, are unable to achieve an effective length corresponding to an ideal dipole and/or are unable to avoid being shielded by other device components or by the body of the wearer. Furthermore, these generally small antennas have limited energy transfer capabilities due to the constraints of the physical size of the paging instrument. Another limitation of these small antennas is that the greatest power transfer to a circuit requires impedance matching with a resonant tuned antenna circuit. The theory of small antennas is further set forth in Small Antennas by Harold A. Wheeler published in IEEE Transactions on Antennas and Propagation, volume AP-23, No. 4, July 1975 and also in Antenna Engineering Handbook, Second Edition, published by McGraw Hill, 1984.
A major design problem for paging instrument antennas has always been how to maximize the antenna sensitivity while minimizing the design complexity and minimizing the interconnection between the antenna(s) and the receiver and/or the transceiver. What is needed is an antenna design which can be utilized to maximize the antenna sensitivity when utilized with the paging device. What is also needed is an antenna design which can be easily changed to provide additional antenna sensitivity when needed. Likewise, an antenna design which can address similar problems associated with the use of cellular telephones is also needed.
The present invention provides unobtrusive and convenient antennas for a wireless communications device that (1) operate as a lanyard, (2) maximize reception, (3) maximize transmission, (4) utilize reasonably broad bandwidths, (5) exhibit good directional characteristics, (6) exhibit the ability to adapt to antenna sensitivity, and (7) conform to the physical constraints of the paging instrument (i.e., the antenna is an appropriate size for the device).
In a first aspect, an antenna of the present invention comprises a lanyard antenna. As utilized herein, the term lanyard generally refers to a flexible cord-like structure of the type generally utilized to secure physical items to an individual.
The lanyard antenna may be attached to a person""s clothing and to the portable communication device where the lanyard will provide an improved antenna and also provide additional security against the portable communications device being dropped. The lanyard antenna need not be disconnected from the person""s clothing for use. Rather, the extension of the lanyard during use of the portable communications device will enhance the receptivity of the antenna, as much of the length of the antenna is situated some distance away from both the person""s body and the communication device.
A lanyard antenna of the present invention is particularly well suited for use with pagers and in particular with interactive messaging pagers. The antenna increases transmission and reception performance and, thereby, increases the operating range of the pagers. The antenna may be a dipole of xc2xd, xc2xc, xe2x85x9, or any wavelength. The antenna further may be center-loaded or end-loaded. It could also take the form of a loop antenna in which both ends are coupled to transmitter circuitry, receiver circuitry, or both.
According to a first embodiment of the present invention a lanyard antenna comprises at least one continuous antenna conductive element that is embedded within a flexible strength member. The total length of the flexible strength member may be longer than the total length of the antenna conductive element.
The flexible strength member is preferably non-binding, non-twisting, and produced from nonconductive material, such as, natural and/or synthetic compositions. The antenna conductive element is preferably formed from at least one distinct wire, wire braid, or wire mesh that is produced from a flexible conductive material, such as beryllium copper, copper, aluminum, iron alloys, or phosphor bronze.
According to a second embodiment of the present invention a lanyard antenna comprises at least one antenna conductive element. The antenna conductive element is preferably formed from at least one distinct wire, wire braid, or wire mesh that is fashionably designed and is produced from a flexible conductive material, such as beryllium copper, copper, aluminum, iron alloys, or phosphor bronze.
In another aspect the present invention comprises a wireless communications device with a lanyard antenna of the present invention. The wireless communications device may comprise a pager, an interactive messaging pager, a telephone (portable, cellular, mobile, satellite, etc.), a PDA, or other wireless communications device.
The objects, features, and advantages of the present invention are described in more detail below with reference to the embodiment depicted in the attached drawings. Further objects, features, and advantages of the present invention will be apparent from the description provided.